Development of Bimetallic PdNi Electrocatalysts toward Mitigation of Catalyst Poisoning in Direct Borohydride Fuel Cells
Sulay Saha, Pralay Gayen, Zhongyang Wang, Ram Dixit, Kritika Sharma, Suddhasatwa Basu, Vijay Ramani
Abstract
Cost-effective and highly active borohydride oxidation reaction (BOR) electrocatalysts are crucial for the advancement of direct borohydride fuel cells (DBFCs). Noble-metal electrocatalysts, such as Pd, are used as benchmark electrocatalysts because of their superior BOR activity. However, Pd suffers from catalyst poisoning because of strong binding with BHx intermediates at a high BOR overpotential, making it unsuitable for high DBFC performance, whereas Ni exhibits a low degree of catalyst poisoning because of a relatively weak binding of BHx intermediates. Density functional theory (DFT) calculations indicate a lowering of H- and OH-binding energies on bimetallic PdNi surfaces in comparison to their individual counterparts, thereby freeing more sites for BH4 adsorption that is crucial for a high BOR rate. The as-synthesized bimetallic PdNi/C electrocatalyst exhibits higher current densities at a BH4 concentration range of 50–500 mM than Pd/C and Ni/C. A DBFC unit with a pH-gradient-enabled microscale bipolar interface employing PdNi/C, Pt/C, and H2O2 as the anode, cathode, and oxidant, respectively, exhibits a power density of 466 ± 1.5 mW/cm2 at 1.5 V, a peak power density of 630 ± 2 mW/cm2 at 1.1 V, with an open-circuit voltage of 1.95 ± 0.01 V. Our bimetallic alloy electrocatalyst shows high DBFC performance, providing a pathway for the development of suitable BOR electrocatalysts.